As promulgated by the International Maritime Organization (IMO), issued as Revised MARPOL Annex VI, marine fuels will be capped globally with increasingly more stringent requirements on sulfur content. In addition, individual countries and regions are beginning to restrict sulfur level used in ships in regions known as Emission Control Areas, or ECAs.
The fuels used in global shipping are typically marine bunker fuels, for larger ships. Bunker fuels are advantageous since they are less costly than other fuels; however, they are typically composed of cracked and/or resid fuels and hence have higher sulfur levels. Meeting the lower sulfur specs for marine vessels can be conventionally accomplished through the use of distillates. However, distillate fuels typically trade at a high cost premium for a variety of reasons, not the least of which is the utility in a variety of transport applications employing Compression ignition engines. They are produced at low sulfur levels, typically significantly below the sulfur levels specified in the IMO regulations.
Those regulations specify, inter alia, a 1.0 wt % sulfur content on ECA Fuels (effective July 2010) for residual or distillate fuels, a 3.5 wt % sulfur content cap (effective January 2012), which can impact about 15% of the current residual fuel supply, a 0.1 wt % sulfur content on ECA Fuels (effective January 2015), relating mainly to hydrotreated middle distillate fuel, and a 0.5 wt % sulfur content cap (circa 2020-2025), centered mainly on distillate fitel or distillate/residual fuel mixtures. When the ECA sulfur limits and sulfur cap drops, various reactions may take place to supply low sulfur fuels. The 0.1% Sulfur ECA fuel can be challenging to supply, since shippers typically purchase tower sulfur fuel oils with properties suitable for marine applications, and at a steep price discount to distillate fuels.
Hydrotreaters in front of fluid catalytic cracking (FCC) units, commonly called CFHT, typically hydroprocess petroleum gasoils and resids to sufficiently low sulfur levels such that the product fuels are sufficient to be sold as fuel with no further treatment, or with minimal incremental hydroprocessing.
It would be advantageous to utilize a fuel high energy content, low sulfur fuels in marine applications, which fuels have conventionally included cracked distillates. Distillates can typically command a much higher value than bunker fuels. An alternative low sulfur marine bunker fuel, with the correct fuel quality characteristics, could command a high premium in the marketplace.
Indeed, there are some publications that disclose the desirability of lowering the sulfur content of marine bunker fuels. A non-exclusive list of such publications includes, for example, U.S. Pat. Nos. 4,006,076, 4,420,388, 6,187,174, 6,447,671, and 7,651,605, U.S. Patent Application Publication Nos. 2008/0093262 and 2013/0340323, PCT Publication Nos. WO 1999/057228 and WO 2009/001314, British Patent No. GB 1209967, Russian Patent No. RU 2213125, Japanese Patent No. JP 2006000726, and the following articles: Chem. & Tech. of Fuels and Oils (2005), 41(4), 287-91; Ropa a Uhlie (1979), 21(8), 433-40; Godishnik na Visshya Khim. heski Institut, Sofiya (1979), 25(2), 146-48; Energy Progress (1986), 6(1), 15-19; and Implications Across the Supply Chain (30 Sep. 2009) Sustainable Shipping Conference in San Francisco, Calif.
Thus, it would be desirable to find compositions (and methods for making them) in which hydrotreated and/or uncracked gasoil products could be used in marine bunker fuels, as described with reference to the invention herein.